Water Bottle Greenhouse For Seedlings

This is perhaps the simplest concept on this entire list. This greenhouse costs you absolutely nothing, and will take about five minutes to make. Now, this isn’t a classic large greenhouse for holding plants well into their maturity, so another design would be needed if that’s your need. Instead, this is a germination greenhouse, meant to support the little seedlings as they sprout up. 

Despite its simplicity, it is very effective at keeping the internal temperature slightly above the ambient temperature, to help the seeds along. This is especially useful for getting a head start on warm-season plants like tomatoes and peppers. The only material you’ll need to make this greenhouse is a clear plastic bottle, along with some kind of cutting tool. That’s it.